## R Code
library(data.table)
library(pipeR)
library(tidyr)

tt = c("BAGFFABFC",
       "BAGFFABFC",
       "xxxFAABCCGBBF",
       "xxxFAABFCGFBF",
       "xxxxGBBFCGFEEBA",
       "xxxxGBBFGGFEEBA",
       "xxxxxxxxxxxxEEBACAEEGFGAA",
       "xxxxxxxxxxxxxxxxxxGFGFAACDABG",
       "xxxxxxxxxxxxxxxxxxGFGFACCDABG")

s1 = sapply(tt,function(x){

  charlen = nchar(x)
  list(
    len = rep(charlen,7), ## 字串長度
    global_charnum = seq(charlen-6,charlen,1), ## 字母在 1 ~ 29 哪個位置
    local_charnum = seq(-7,-1,1),              ## 字母在 -1 ~ -7 哪個位置
    stri = unlist(strsplit(gsub("(.{1})","\\1 ",substr(x,charlen - 6, charlen)),split=" ")) ## 將後7個字母切開

  )

},USE.NAMES = F) %>>% (apply(X=.,MARGIN=1,function(x) do.call(cbind,x))) %>>% data.table %>>%  ## 組成字母在哪個位置的資料格式 (data.table)
  `[`(,c("stri","local_charnum","numer") := list(factor(stri),factor(local_charnum),1)) %>>% ## numer 為分子 初始為 1
  unique ## distinct 相同字串長度、字母、位置

s2 = s1 %>>% `[`(,.N,by=c("global_charnum","stri"))

s3 = merge(s1,s2,by=c("global_charnum","stri"),all.x=T)  %>>% ## By glocbal_charnum, stri 作 left join
  `[`(,.(len,global_charnum,local_charnum,stri,val = numer/N)) %>>% ## val = numer/N 為矩陣內的值
  (split(x=.,f=.$len)) %>>%  ## By 字串長度切割成 list 格式
  (lapply(X=.,FUN = function(x){
    x %>>% `[`(,.(local_charnum,stri,val)) %>>% (spread(data=.,local_charnum,val,drop=F,fill=0)) ## long 轉 wide 格式
    }))